Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having at least one of copying, printing, scanning, and facsimile capabilities, typically form an image on a recording medium according to image data. Thus, for example, a charger uniformly charges a surface of an image bearing member; an optical scanner projects a light beam onto the charged surface of the image bearing member to form an electrostatic latent image on the image bearing member according to the image data; a developing device supplies toner to the electrostatic latent image formed on the image bearing member to render the electrostatic latent image visible as a toner image; the toner image is directly transferred from the image bearing member onto a recording medium or is indirectly transferred from the image bearing member onto a recording medium via an intermediate transfer member; a cleaning device then cleans the surface of the image carrier after the toner image is transferred from the image carrier onto the recording medium; finally, a fixing device applies heat and pressure to the recording medium bearing the unfixed toner image to fix the unfixed toner image on the recording medium, thus forming the image on the recording medium.
Among known optical scanners, a long-length lens employed in the optical scanner is held by a lens support substantially at the bottom center of the long-length lens. Variation in parts and parts placement, or variation in frictional force due to a difference in a surface roughness of parts in the optical scanner causes a pressure applied to an upper surface of the lens to differ from that applied to a bottom surface thereof. As a result, the lens may not contact the surface of the lens support, which is supposed to contact the surface of the lens to hold the lens in place, but instead leaves an undesirable minute gap between the lens and the lens support.
Such a minute gap permits the lens to move undesirably when fastening an adjusting screw that presses the lens to adjust the shape of the lens. A change in the position of the lens changes the curve of the lens when the lens is subjected to shock or during adjustment, thereby changing a scan line of light passing through the lens. Generally, an optical lens requires fine adjustment by several tens of micrometers. Hence, prevention of such displacement of the lens is crucial. A plurality of screws may be used to fix the lens in place more reliably, but at the cost of increasing the number of constituent parts and manufacturing steps.
In such an optical scanner, a spring may be used to support the lens in place. Depending on the spring and the lens, however, it may be difficult to apply stress straight in the direction of adjustment, which requires high-precision parts and assembly. Where stress is not applied properly, adjustment by the screw cannot be performed linearly and/or the lens support does not contact the lens in the pressing direction, thereby causing displacement of the lens.
Furthermore, using a plurality of springs or other elastic members further complicates assembly.